=over

=item shmctl ID,CMD,ARG
X<shmctl>

Calls the System V IPC function shmctl.  You'll probably have to say

    use IPC::SysV;

first to get the correct constant definitions.  If CMD is C<IPC_STAT>,
then ARG must be a variable that will hold the returned C<shmid_ds>
structure.  Returns like ioctl: L<C<undef>|/undef EXPR> for error; "C<0>
but true" for zero; and the actual return value otherwise.
See also L<perlipc/"SysV IPC"> and the documentation for
L<C<IPC::SysV>|IPC::SysV>.

Portability issues: L<perlport/shmctl>.

=back